Gas seal members such as packing and gaskets are conventionally used as members for preventing air leakage. Such gas seal members are then used, for example, for apparatuses that mine underground resources such as petroleum and natural gas at great depth or for hydrogen stations for fuel cell vehicles. In such applications, gas sealing members will be exposed to a harsh environment such as a high temperature environment or the like. Thus, a higher durability in a high temperature environment is required for gas seal members.
For example, in PTL1, a gas seal member that is durable under harsh conditions such as a high temperature environment or the like over a long period of time is provided by forming a gas seal member through crosslinking of an elastomer composition that is obtained by blending multi-walled carbon nanotubes having a specific average diameter relative to a three-dimensional fluorine-containing elastomer in a predetermined proportion.